The present invention relates to a wind-up projection screen which receives image lights coming from projectors such as the overhead projector (OHP), the CRT video projector, the liquid crystal projector or the like and, particularly, to a projection screen which assures the optimum luminance, contrast, color reproduction or the like in accordance with the brightness of a location or the luminance of a projector to be used.
There was conventionally proposed a typical projection screen 21 as shown in FIG. 5 which is suspended from the ceiling while a projector 23 placed on a floor stand projects image lights therefrom towards the screen 23 for spectators"" view.
The surface of this projection screen is subjected to a delustering treatment (by means such as dulling or matting finish) to insure that the image lights are scattered (for forming an image). There was further provided a type having its surface subjected to embossing to insure that the projector operates to centrally direct the projection lights otherwise scattering in upward and downward directions while centrally directing the projection lights otherwise scattering in right and left directions such that the screen gain attains the level of 10 or more (which is ten times the reflection rate of the standard white).
So far, the progress in the recent development of the projector 23 is remarkable and the values showing the brightness or luminance thereof has continued to rise to such an extent that some projector attained the brightness thereof which has become 30 or more times those of the primitive CRT projectors (for example, 1500 ANSI lumen). Therefore, the long lasting method for projection within a dark room is no longer necessary because projection is possible even in a bright living space.
However, no matter how the brightness of the image lights projected by the projector is increased, lights E coming from an illumination appliance or through windows from outside in an ordinary living are reflected in the form of white lights by the projection screen 21 space to reach the spectators such that the image lights formed by the projector screen 21 are mixed with said white lights because the projection screen itself looks white.
As a result, the projected image with high luminance can become cloudy or nebulas in its entirety unlike the original image to mar the color reproduction or contrast in the image. Particularly, since black can turn into gray to make letters or symbols illegible against white shining with high luminance and the higher luminance the weary eye results.
The problem to be solved by the present invention is to provide a projector screen which is capable of forming a high quality image with a high luminance projection lights even in a bright space as well as with a low luminance projection lights in a dim location.
The present invention essentially provides a projection screen comprising a first image forming film of a colorless transparent soft resin, said first image forming film having a face side and a reverse side, said face side being delustered and embossed such that horizontally and vertically reflected lights are centrally directed, a second image forming film of gray colored transparent soft resin, said second image forming film having a face side and a reverse side, said face side being delustered and embossed such that horizontally and vertically reflected lights are centrally directed; said first and second image forming films being of an equal thickness and hardness; and a non-stretchable mirror surface film sandwiched and bonded between said reverse side of the first image forming film and said reverse side of the second image forming film.